Heavy metals biosorption by Thapsia transtagana stems powder: Kinetics, equilibrium and thermodynamics

The present study investigates the biosorption potential of natural and low-cost biosorbent Thapsia transtagana stems (TTS) form for the removal of cadmium (II) and cobalt (II) ions from aqueous solution. The surface of TTS has been thoroughly characterized by FTIR spectroscopy, scanning electron microscopy–energy-dispersive X-ray spectroscopy, Boehm titration, and point of zero charge. Batch biosorption experiments were carried out to evaluate the effect of process parameters, viz solution pH, biosorbent dosage, contact time, initial metal ion concentration and temperature on the biosorption of Cd(II) and Co(II) ions using the biosorbent. Experimental results show that, the biosorption process is very rapid and the biosorption yield increases with an increase in biosorbent dosage. Maximum biosorption was occurred at pH between 6 and 7. Kinetic data were properly fitted with the pseudo-first-order model instead of pseudo-second-order model. Biosorption isotherms were best correlated with Langmuir model than with Freundlich model. The biosorption of the metals ions was exothermic in nature (ΔH° = –20.10 kJ/mol for Cd(II) and –20.87 kJ/mol for Co(II)). When the temperature was increased from 25°C to 55 °C, the reaction was accompanied by a decrease in entropy (ΔS° = –73.42J/K.mol for Cd(II) and –84.38 J/K.mol for Co(II))

New Sustainable Biosorbent Based on Recycled Deoiled Carob Seeds: Optimization of Heavy Metals Remediation

In this study, an efficient biosorbent was developed from deoiled carob seeds, a agroindustrial waste. The biosorption efficiency was evaluated for cadmium and cobalt ions removal from aqueous solution under various parameters such as treating agent, solution pH, biosorbent dosage, contact time, initial metal ions concentration, and temperature. The effect of some major inorganic ions including Na+, K+, Ca2+, Mg2+, and Al3+ on the biosorption was also established. Based on this preliminary study, four independent variables including solution pH, biosorbents dosage, initial metal concentration, and treating agent were chosen for the optimization of the process using full-factorial experimental design. It was found that chemical pretreatment of the raw deoiled carob seeds with NaOH strongly enhances its biosorption potential. Thus, the optimal conditions for high biosorption of cadmium(II) and cobalt(II) were achieved at pH of 6, biosorbent dosage of 1 g/L, and initial metal concentration of 50 mg/L. The biosorbents were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Boehm titration, and the point of zero charge (pHPZC)

Adsorption behavior of methylene blue onto powdered Ziziphus lotus fruit peels and Avocado kernels seeds

In this research, two agroforestry by‐products were used as adsorbents for the removal of methylene blue (MB), as a model dye, from aqueous solution. The Ziziphus lotus fruit peels (ZLP) and Avocado kernel seed (AKS) were dried and powdered to particles of sizes <125 μm. Adsorption study was carried out in batch mode under different condition by varying initial dye concentration, contact time, initial solution pH, adsorbent dosage and reaction temperature. Rate constants of the adsorption were calculated by kinetic measurements. Equilibrium data were correlated to Langmuir and Freundlich isotherm models. The best fit was obtained by Langmuir model with maximum monolayer adsorption capacities of 66.04 mg/g in the case of ZLP and 59.07 mg/g in the case of AKS. The surface properties of the adsorbents were characterized by FTIR spectroscopy, SEM‐EDX analysis and the point of zero charge

Novel Ag-ZnO-La2O2CO3 photocatalysts derived from the Layered Double Hydroxide structure with excellent photocatalytic performance for the degradation of pharmaceutical compounds

In this work, we have prepared the Ag-ZnO-La2O2CO3 nanomaterials as promising photocatalysts for the photocatalytic degradation of pharmaceutical pollutants. Firstly, a series of ZnAl1-xLax(CO3) (0 ≤ x ≤ 0.5) layered double hydroxides (LDHs) were synthesized by the co-precipitation method at the component molar ratio of Zn/(Al + La = 3, where La/Al = 0, 0.25 and 0.5). Photocatalysts were prepared by the calcination of the LDH precursors at different temperatures of 300, 400, 500, 600, 800 and 1000 °C. The effects of the La/Al molar ratio and the calcination temperature on the photocatalytic activity of the catalysts were evaluated by the degradation of caffeine as a model pharmaceutical pollutant in aqueous solutions under the UV irradiation. Thereafter, in order to increase the photocatalytic activity, the catalysts obtained at the optimal La/Al molar ratio and calcination temperature were doped with the Ag noble metal at various concentrations (i.e. 1, 3 and 5 wt%) using the ceramic preparation process to obtain the desired Ag-ZnO-La2O2CO3 catalysts. The synthesized photocatalysts were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) coupled with energy dispersive X-ray analysis (EDX) and UV-visible diffuse reflectance spectroscopy (UV-Vis DRS). Detailed photocatalytic experiments based on the effects of the irradiation time, the dopant amount, the catalyst dose, the initial solution pH and reuseability were performed and discussed in this study. The Ag doped material showed significantly a higher photocatalytic activity compared to the undoped, pure ZnO and P-25 catalysts. The experimental results show that the highest photocatalytic activity was obtained from the Ag (5%) doped Zn-0.75Al-0.25La-CO3 photocatalysts calcined at 500 °C with a degradation efficiency of 99,4% after 40 min of irradiation only. This study could provide a new route for the fabrication of high performance photocatalysts and facilitate their application in the environmental remediation issues. Keywords: Layered double hydroxides, Photocatalyst, Doping, Photocatalytic degradation, Caffein

Defluoridation of groundwater by calcined Mg/Al layered double hydroxide

The present study evaluated calcined Mg/Al layered double hydroxide (CLDH) availability for the removal of fluoride from local groundwaters. The Mg/Al layered double hydroxide (LDH) was synthesized by co-precipitation method and characterized by XRD, FT-IR and TGA-TDA analyses. Batch defluoridation experiments were performed under various conditions such as calcination, solution pH, contact time, temperature, material dosage and reuse. Experimental results indicate that fluoride removal strongly increased after calcination of the LDH up to 600 °C. The maximum fluoride removal was obtained at solution pH of 6.85. Kinetics of fluoride removal followed the pseudo-second order kinetic model. The rise in solution temperature strongly enhances the removal efficiency. The adsorption mechanism involved surface adsorption, ion exchange interaction and original LDH structure reconstruction by rehydration of mixed metal oxides and concomitant intercalation of fluoride ions into the interlayer region. The optimum dosages required to meet the national standard for drinking water quality were found to be 0.29 and 0.8 g/L, respectively, for Bejaad and Settat goundwaters. A decrease in the fluoride uptake with increasing the number of regeneration cycles was observed

Effectiveness of beetroot seeds and H3PO4 activated beetroot seeds for the removal of dyes from aqueous solutions

Raw beetroot seeds (BS) and H3PO4 activated beetroot seeds (H3PO4-BS) were evaluate for their effectiveness in removing methylene blue (MB) and malachite green (MG) from aqueous solution. BS were carbonized at 500°C for 2 h, and then impregnated with phosphoric acid (phosphoric acid to BS ratio of 1.5 g/g). The impregnated BS were activated in a tubular vertical furnace at 450°C for 2 h. Batch sorption experiments were carried out under various parameters, such as solution pH, adsorbent dosage, contact time, initial dyes concentration and temperature. The experimental results show that the dye sorption was influenced by solution pH and it was greater in the basic range. The sorption yield increases with an increase in the adsorbent dosage. The equilibrium uptake was increased with an increase in the initial dye concentration in solution. Adsorption kinetic data conformed more to the pseudo-second-order kinetic model. The experimental isotherm data were evaluated by Langmuir, Freundlich, Toth and Dubinin–Radushkevich isotherm models. The Langmuir maximum monolayer adsorption capacities were 61.11 and 74.37 mg/g for MB, 51.31 and 213.01 mg/g for MG, respectively in the case of BS and H3PO4-BS. The thermodynamic parameters are also evaluated and discussed

Activated carbon from Thapsia transtagana stems: central composite design (CCD) optimization of the preparation conditions and efficient dyes removal,166, 259–278

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Factorial experimental design for the optimization of catalytic degradation of malachite green dye in aqueous solution by Fenton process

This work focuses on the optimization of the catalytic degradation of malachite green dye (MG) by Fenton process “Fe2+/H2O2”. A 24 full factorial experimental design was used to evaluate the effects of four factors considered in the optimization of the oxidative process: concentration of MG (X1), concentration of Fe2+ (X2), concentration of H2O2 (X3) and temperature (X4). Individual and interaction effects of the factors that influenced the percentage of dye degradation were tested. The effect of interactions between the four parameters shows that there is a dependency between concentration of MG and concentration of Fe2+; concentration of Fe2+ and concentration of H2O2, expressed by the great values of the coefficient of interaction. The analysis of variance proved that, the concentration of MG, the concentration of Fe2+ and the concentration of H2O2 have an influence on the catalytic degradation while it is not the case for the temperature. In the optimization, the great dependence between observed and predicted degradation efficiency, the correlation coefficient for the model (R2=0.986) and the important value of F-ratio proved the validity of the model. The optimum degradation efficiency of malachite green was 93.83%, when the operational parameters were malachite green concentration of 10 mg/L, Fe2+ concentration of 10 mM, H2O2 concentration of 25.6 mM and temperature of 40 °C

Dye removal from aqueous solution by raw maize corncob and H3PO4 activated maize corncob

The focus of this study is the investigation of removal ability of methylene blue (MB) and malachite green (MG) dyes from aqueous solution by raw maize corncob (RMC) and H3PO4 activated maize corncob (AMC). Maize corncobs were carbonized at 500 °C for 2 h, and then impregnated at a phosphoric acid to maize corncob ratio of 2.5 g/g. The impregnated maize corncob was activated in a tubular vertical furnace at 450 °C for 2 h. Samples were characterized by different methods. Adsorption experiments were carried out as a function of solution pH, adsorbent dosage, contact time, initial concentration of dyes and the temperature. Experimental results show that the activation of maize corncob boosts four times the adsorption performance for the selected dyes. The adsorption process is very rapid and was pH dependent with high adsorption capacities in the basic range. The kinetic data were fitted with the pseudo-second-order kinetic model. The best fit of equilibrium data was obtained by the Langmuir model with maximum monolayer adsorption capacities of 75.27 and 271.19 mg/g for MB, 76.42 and 313.63 mg/g for MG, respectively, in the case of RMC and AMC. The temperature did not have much influence on the adsorption performance

Photocatalytic degradation of 2,4-D and 2,4-DP herbicides on Pt/TiO2 nanoparticles

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